This study is a comprehensive analysis of the appropriate clinical use of prenatal diagnostic tests for chromosomal abnormalities, focusing on amniocentesis and chorionic villus sampling (CVS). This investigation will assess how decisions regarding these tests air, currently being made, and will generate information which could be used for two purposes: 1) to formulate clinical guidelines for prenatal diagnosis using a preference-based approach and 2) to develop a decision-assisting methodology to assist women and partners in making prenatal diagnosis decisions. The study is divided into three discrete but related tasks which will be carried out jointly by the University of California, San Francisco (UCSF), and the Technology Assessment Group. The three tasks are: 1) a nationwide survey of practitioners to assess the current knowledge, attitudes and practices with respect to these tests; 2) measurement of patient utilities associated with the varying outcomes of these tests; and 3) conduct of a series of cost-benefit, cost-effectiveness, and cost-utility analyses. During Task 1, a mail survey of a regionally stratified sample of obstetricians, family practitioners, and genetic counselors will be performed to assess variation in knowledge and attitudes about indications for and capabilities of prenatal diagnosis. Practitioners' thresholds for recommending prenatal diagnosis and independent predictors of high and low utilizers will be identified. Task 2 will consist of detailed interviews with obstetrical patients undergoing genetic counseling at UCSF to assess utilities associated with discrete components of the decision to undergo a prenatal diagnostic procedure. Utilities of common sequences of states associated with prenatal diagnosis will also be measured to provide information on preferences and quality of life associated with outcomes of prenatal diagnosis. During Task 3, a series of economic analyses will be conducted. Using data obtained from practitioners' surveys, patient interviews, the published literature, a survey of prenatal diagnosis centers, existing databases, the billing office of UCSF, and expert opinion, a series of analyses will be conducted to assess the expected cost benefit, cost effectiveness and cost utility associated with these diagnostic tests under alternative scenarios. The information generated and the analyses performed during this investigation will provide the necessary groundwork for the development and implementation of preference-based clinical guidelines for the use of prenatal diagnostics.